When observation is conducted on a deep part of a living organism during observation with a microscope, an S/N ratio of an mage undergoes deterioration due to effects of feedback light rays from other than a focal plane. This phenomenon cannot be sufficiently removed even with the use of a confocal microscope.
Techniques for solving this problem (refer to U.S. Pat. No. 5,973,828, U.S. Pat. No. 5,969,854, U.S. Pat. No. 6,423,956, DE4326473) have been proposed.
With those techniques, 2 units of objective lenses are employed to be disposed such that respective focal regions intersect each other, combination of such a layout with confocal microscope techniques enabling information on an intersected region only to be obtained, thereby enhancing primarily resolution depthwise (refer to FIG. 2, U.S. Pat. No. 5,973,828) although horizontal resolution undergoes deterioration to some extent.
In Non-patent Document 2, it has been described that a structure made up of lenses relatively low in NA has advantageous effects as follows:
(1) Resolution in the direction of the optical axis is enhanced.
(2) In observation on deep parts of a living organism, aberration is insusceptible to occur because NA is small.
(3) Components small in diameter can be fabricated with greater ease.
(4) Since WD can be rendered longer, the structure is suited for observation on the deep parts.
(5) Since two optical paths are separate from each other, observation on the deep parts is insusceptible to effects of noise rays such as rays of feedback light from other than an observation plane, and so forth.
Further, in FIG. 7 of U.S. Pat. No. 5,973,828, there has been disclosed a scanning mechanism for scanning respective positions of focal points while keeping positional relation between two objective lenses. Still further, in Non-patent Document 1, and Non-patent Document 2, there has been disclosed a method for scanning while moving an object with the use of a stage, and so forth.
[Patent Document 1] U.S. Pat. No. 5,973,828
[Patent Document 2] U.S. Pat. No. 5,969,854
[Patent Document 3] U.S. Pat. No. 6,423,956
[Patent Document 4] German Patent No. 4326473
[Non-patent Document 1] “Confocal microscope with large field and working distance”, Applied Optics, Vol. 38, No. 22, pp. 4870
[Non-patent Document 2] “Dual axis confocal microscope for high resolution in vivo imaging”, Optics Letters, Vol. 28, No. 6, pp. 414